Automatic air painting apparatus

ABSTRACT

Automatic air painting apparatus for painting precision stripes on relatively large, elongated workpieces. The workpieces are moved past an airbrush assembly by a conveyor mechanism. As they pass under the airbrush, the workpieces contact a roller which lifts the airbrush nozzle above the surface of the workpiece and holds it at a predetermined spacing in spite of variations in the height of the workpieces. When the roller is lifted by the leading edge of the workpiece, it actuates a microswitch that turns the airbrush on, and when the roller drops off the trailing edge of the workpiece, it automatically turns the airbrush off by releasing the same microswitch. To minimize inertia, the roller is positioned so as to contact the airbrush nozzle directly instead of being linked to the airbrush by a mechanical linkage, and the airbrush is mounted on a balanced, spring-loaded rotary mounting which enables it to respond very quickly to changes in the position of the roller. Two parallel airbrush assemblies and conveyor mechanisms are mounted on a common base and are driven by a single motor and supplied by a common source of paint and compressed air.

United States Patent [72] Inventors Jens A. Paasche, deceased late of Wilmette, 111.; Continental Illinois National Bank and Trust Company 01' Chicago, executor, 231 S. LaSalle St., Chicago, Ill. 60604 [21] Appl. No. 855,783 [22] Filed Sept. 5, 1969 [45] Patented July 20, 1971 [54] AUTOMATIC AIR PAINTING APPARATUS 14 Claims, 9 Drawing Figs.

[52] U.S.Cl [18/2, 118/8, 118/315, 118/323 [51] Int. Cl B05c 11/00 [50] Field of Search 118/2, 8, 323, 321, 315, 316, 410,41 1, DIG. 9

[56] References Cited UNITED STATES PATENTS 2,144,263 1/1939 Lane 118/411 X 2,252,431 8/1941 Klammt 118/2 X 3,548,456 4/1951 Wells 118/411 X 3,424,836 l/l969 McKelvey ABSTRACT: Automatic air painting apparatus for painting precision stripes on relatively large, elongated workpieces. The workpieces are moved past an airbrush assembly by a conveyor mechanism. As they pass under the airbrush, the workpieces contact a roller which lifts the airbrush nozzle above the surface of the workpiece and holds it at a predetermined spacing in spite of variations in the height of the workpieces. When the roller is lifted by the leading edge of the workpiece, it actuates a microswitch that turns the airbrush on, and when the roller drops off the trailing edge of the workpiece, it automatically turns the airbrush off by releasing the same microswitch. To minimize inertia, the roller is positioned so as to contact the airbrush nozzle directly instead of being linked to the airbrush by a mechanical linkage, and the airbrush is mounted on a balanced, spring-loaded rotary mounting which enables it to respond very quickly to changes in the position of the roller. Two parallel airbrush assemblies and conveyor mechanisms are mounted on a common base and are driven by a single motor and supplied by a common source of paint and compressed air.

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This invention relates to automatic air painting apparatus 5 I and more particularly to automatic air painting apparatus for painting stripes on relatively large, elongated workpieces such as strips of'aluminum molding material or the like."

[Automatic airpainting apparatus has been devised in the pastfor painting stripes on varioustypes of workpieces, but

although these prior art painting devices have beensuccessful whenjused in connection with a variety of different shaped workpieces, serious diffic ul'ties have been encountered inconnection withreiatively large, elongated workpieces such as strips of-"aluminummoldingor the like.

x One difficulty relates to variations in 'the dimensions of the u 1 workpieces. The prior art painting devices have been designed for operation in connectionwith .workpieces having fixed dimensions, 'and they require relatively precise adjustment difficultyin that molding-is manufactured inva variety of dit} 1 ferent widths arid thicknessss-Accordihglyj one object of this invention isto provide automatic painting apparatus fo'r'paint ing preCisionstripes on elongated workpieces ofvariable dimensions in which the adjustment for different dimensions is performed automatically Another difficultyrrelates' tothemeans ffor conveying the workpieces past the-airbrushas'sembly. Theprior art auto- 'matic painting devices have been designed-to function as part of anassembly line where painting is performed as one step in a, continuous manufacturing process, ,In the manufacture of aluminum molding, however, painting cannotrbe performedas apart of th'e manufaeturing process because the siding is too hot tobe painted when it emerg'es'fromthe itinal rolling mill station and the individual pieces-of moldingemerge from the rolling-mill at such a high {rate'that they cannotbe conveni ently cooledina conveyor prior to painting. Accordingly, the individual vpiecespf moldingare stacked inpiles at the end of the rolling mill-andQthepainting'operation must be per,-

formed a'safseparate operationlater. This means that-theconveyor. mechanism for the painting apparatus'im ust be adapted to accept and ha ndle molding strips that are. inserted manually fromqa'pile of such stripsnear the apparatus,"and itfis afurther object aof this invention to ,provide ;such'-.a {conveyor Other'difficultiesencountered with relativelyfll arge, siengated workpieeessuch aluminum moldinjgzinvolve physical wear of the conveyor mechanism, and. it isan additional object I of this invention to provide aconveyor mechanism that is rugged in construction and long-lasting in operation.

' isUMM RvoFTHE INVENTION y j 'QIn accord a ncewith this-invention, the above-noted objects I are achievedlbyproviding a low-inertia airbrush mounting structurein which a roller-rides directly" on top ofthe' workpiece'artd supports the airbrush .nozzle at a predetermined spacing abovethe workpiece by means of direct contact with 3 the nozzle of the airbrush. Theairbrush assembly is mounted on a balanced spring-loaded rotary mounting-which enables it to respond very quickly to changes inthe position of the roller.

When the leadingedge of the: workpiece passes under the roller it lifts the roller and positions. therairbrush nozzle atthe 5 correct spacing and. maintains it at the' 'co'rrect spacing by -'direct contact between theairbrush and'the upper surface of the workpiece. At the same time, the lifting of the roller actuates a microswitch that turns the airbrush on..When the'roller drops off the trailing edge of'the workpiece; it automatically switches the airbrush off. The workpieces are driven under the t airb rush assembly bya plurality of drive rollers and opposing 'pressurerollers which are spaced alonga Teflon runway. Two

position.

. u 20 every time the'dimensionsof the workpieces are changed. In

. painting'stripes on aluminum molding, this presents-a serious pieces undemeath'the airbrush nozzle.

brush switching means so that two workpieces can be painted simultaneously. The drive rollers are all powered from a single DESCRIPTION OFTHEQ DRAWINGS FIG. 1 is an overall-plan view of oneembodiment of the in vention. '1

FIG. 2.is an elevation view ofthe embodiment shown in FIG. 1.

FIG. 3

I H .an enlarged cross-sectional ,view taken along the. plane3 3 ofFIG. 2.

FIG.3. g

FIG. 5 is an enlarged perspective view of one airbrush mounting assembly and the conveyor'means for driving worktaken along the plane 6-6 of FIG. 5.

' FIG. 7 is a side view of an'airbrush assembly in its rest posi- FIG. 9 is a piping diagram showing the pressed-air connections forthe two airbrushes.

DETAILED DESCRIPTION brush and-workpiece conveyoras'semblies for'independently performing the same operation. The details of the mounting structure for the airbrushand conveyor assemblies are, however, more clearly'shown in FIGS. 5 through 8 and the basic operation of the. invention will accordingly be initially described with reference to those figures.- Referring to FIGS, 5 through 8, a relatively large, elongated workpiece l0 is driven underneath an airbrush mounting structure by means of drive rollers l2, l4, and 16 and opposing springloaded idler rollers 18', 20, and 22. The workpiece 10 which is illustrated in FIG. 5 is piece of aluminum molding material which has been grooved inoiie edge and which is to be precisely painted along the bottom of the groove. When the workpiece 10 is inserted between driveroller l2 and idler roller 18, it is moved toward the airbrush assembly by the rotation of drive roller 12 until it contacts a horizontal roller 24 which bears directly against nozzle 30 and tilts the nozzle upwardly as shown in FIG. 8 and holds it a predetermined distance above the top edge of workpiece 10. Horizontal roller 24 rides directly on top of workpiece 10 and bears directly against the nozzle 30 of the airbrush assembly so that the correct spacing between the nozzle and. the top of the workpiece is maintained regardless of any variations in the height of the workpiece. Horizontal roller 24 is journaled on a switch arm 26 .that actuates a microswitch 28 when it is raised toturn the airbrush on and start the painting operation. When the trailing edge. of workpiece '10 passes under roller 24, the switch arm 26 drops, deactuating microswitch 28 and turning the airbrush off. The mounting ar- ,rangement for i the airbrush assembly is spring loaded downwardly, as will be described in detail below, and the I mounting assembly for the airbrushisarranged for minimum inertia so that airbrush nozzle 30 can move very quickly in response to movements of roller 24.

The airbrush housing 32 is joumaled :near its center of gravi-' j ty to a supporting rod 34 which passes through a sleeve 36.

The. sleeve 36 is'welded to the airbrush housing 32 near its center of gravity and. contains a slot 38 for receiving a pin 40 which is inserted'into rod 34. Pin'40 abuts against the two ends FIG. 4 is an enlargedplan view taken along the plane 4-4 of FIG. 8 shows the brush assembly of FIG. in its operative fluid and css about supporting rod 34. A torsion spring 42 is coupled between the end of rod 34 and the end of sleeve 36 to normally urge the airbrush housing 32 downwardly. The tension of torsion spring 42 is adjustable by means of a manual adjustment screw 44.

The airbrush support rod 34 is supported by means of a vertical support rod 46 which is slidably attached to a housing 48. The housing 48 in turn is attached to the side of the machine and contains an adjustment screw 50 which can be loosened to adjust the height of the supporting rod 46 to set the airbrush higher or lower with respect to the base ofthe machine.

The paint supply for the airbrush is provided through a manifold 52 which receives paint through a hose 54 and delivers the paint to the two airbrushes of the machine through flexible hoses 56 and 58. Hose 56 is shown connected to the airbrush housing 32 in FIG. 5, and although the connection of the other paint hose 58 is not specifically shown in FIG. 5, it will be understood by those skilled in the art that hose 58 supplies paint to the other airbrush in a like manner. The compressed-air input for airbrush housing 32 is supplied through a flexible airhose 60 by means of a switch-controlled, compressed-air system which is shown in FIG. 9 and which will be described in later paragraphs.

Referring again to FIGS. through 8, the workpiece slides upon a Teflon runway 62 which is mounted upon the metal base of the machine and is guided by Teflon guides 64, 65, and 66 (FIG. 5) which are mounted in corresponding housings 68, 69 and 70 along the lateral edges of the Teflon runway 62. This insures that the aluminum workpiece 10 will slide along the runway with a minimum of friction and a minimum of wear on the supporting surfaces. To prevent the workpiece from tilting upwardly as it slides along the Teflon runway, a roller 72 is mounted near the airbrush assembly to hold the top of the workpiece down as best shown in FIGS. 5 and 6. Since the stripe which is painted on the upper edge of workpiece 10 is painted in a groove, there is no contact between the roller 72 and the painted surface. A guardrail 73 extends along the Teflon runway opposite the Teflon guides 64, 65, and 66 as best shown in FIG. 6.

FIG. 9 shows the switching circuit for switching the airbrushes off and on at the suitable times to initiate and terminate the painting operation. A paint supply 74 is connected through a flexible hose 54 to a paint manifold 52 which has been described above. Flexible hoses 58 and 56 apply the paint to the two airbrushes independently so that both are continuously supplied with paint. The air supply for the two airbrushes is, however, controlled by independent microswitches to coordinate the application of compressed air with the passage of workpieces underneath the airbrushes so that the airbrushes can be operated independently of each other. Referring to the airbrush 32, which is controlled by the roller 24 and microswitch 28, the output of microswitch 28 is wired to a solenoid 78 which controls an air valve 80 that switches the compressed-air supply to airhose 60 for supplying compressed air to the airbrush 32. When the microswitch 28 is actuated by the passage of a workpiece 10 under roller 24, solenoid 78 opens valve 80 and applies compressed air to the airbrush 32 to commence the painting operation. When the trailing edge of the workpiece 10 passes under the roller 24, the weight of the roller plus the downward urging of the torsion spring 42 on the airbrush mounting assembly causes microswitch 28 to open, thereby closing valve 80 and terminating the air supply to airbrush 32. The air supply to the other airbrush 32 is controlled in the same manner by a microswitch 28 and solenoid valve 80 which is identical to that described above for airbrush 32 and hence will not be described in detail. Suffice it to say that the two airbrushes operate in the same manner but independently of each other in response to passage of workpieces thereunder.

The provision of two independent parallel airbrush assemblies and workpiece feed channels is a particularly important feature of this invention because it permits a single operator to achieve maximum rates of production. In the operation of this ing a workpiece that was previously inserted in the first conveyor channel. By this inserting the workpieces alternately into the two conveyor channels, the operator's time is most effectively utilized and a production rate of approximately twice the number of workpieces per man-hour is achieved as compared to the case where a single conveyor channel is employed.

The drive means for applying a rotary drive force to the drive rollers 12, 14, I6, and the corresponding drive rollers l2, l4, and 16' for the other conveyor channel is shown in FIGS. 1 through 4. Referring to FIGS. I through 4, the bed of the machine comprises a pair of downwardly depending side members 82 and 84 which are connected together by crossmembers 86, 88, 90, 92 and 93. The side members 82 and 84 are rigidly joined together by the crossmembers 86 through 93 and the rigid frame formed thereby is supported by six legs, three of which are shown in FIG. 2. A pair of rectangular channel members 94 and 96 (FIG. 3) are mounted in spaced parallel relationship across the crossmembers 86, 88, 9f), 92 and 93 to support the two parallel workpiece conveyor channels.

All of the driven rollers 12, I2, 14, 14, 16, and 16 are ar ranged to be driven from a single electric motor by means of a gear and drivebelt arrangement which is discussed below.

As best shown in FIG. 2, a mounting bracket 98 extends between the two central legs of the assembly for supporting a motor 100. The motor 100 is linked by a belt 101 to a worm gear assembly 102 that turns a vertical drive shaft 104. Shaft 104 extends upwardly and drives the roller 14 directly. A pulley assembly 106 having openings therein for two drivebelts is attached to shaft 104 for driving the remaining driven roller assemblies. As best shown in FIG. 4, the upper belt 108 on pulley 106 is looped around the drive pulleys for rollers 14', 16', and 16. The lower drivebelt 110 loops around in the opposite direction to drive the pulleys l2, l2, and 14'. It will be seen in this arrangement that a double pulley 112 is required for the drive shaft of drive roller 14' since this roller receives a drive thrust from both of the belts 108 and 110.

A pair of adjustable tension rollers I14 and 116 are mounted for adjusting the tension in the two drivebclts 108 and 110 as best shown in FIG. 4.

The foregoing belt drive system is a particularly important feature of this invention inasmuch as it enables all six of the driven rollers to be powered from the same motor in an extremely simple and rugged drive assembly. From the foregoing description it will be apparent that this invention provides apparatus for automatically painting precision stripes on workpieces at relatively high rates of production. And although this invention has been illustrated with reference to one specific example, it should be understood that this invention is not limited to the detailed structures which have been shown in the drawings and described above since many obvious modifications can be made in those structures to adapt the apparatus for different types of workpieces or for different painting applications. Many such modifications will be apparent to those skilled in the art, and it should be understood that this invention includes all modifications falling within the scope of the following claims.

I claim:

1. Automatic air painting apparatus comprising a supporting structure, an airbrush having a nozzle and means for ejecting a flow of paint from said nozzle in response to the application of compressed air thereto, said airbrush being journaled to said supporting structure for rotation about an axis transverse to the axis of said nozzle, means for moving elongated workpieces past the nozzle of said airbrush, means urging the rotation of said airbrush about its journal axis toward said elongated workpieces, a spacing roller positioned to be engaged by said elongated workpieces as they pass the nozzle of said airbrush, said roller being coupled to the nozzle of said airbrush and being operable to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces as they move past said nozzle, and means coupled to said roller for applying compressed air to said airbrush when said roller is engaged by any one of said elongated workpieces, thereby applying a flow of paint to said adjacent surfaces of said elongated workpieces as they are moved past the nozzle of said airbrush.

2. Automatic air painting apparatus as defined in claim I wherein said spacing roller is positioned to make direct contact with the nozzle of said airbrush to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces.

3. Automatic air painting apparatus as defined in claim 1 wherein said last-mentioned means comprises a source of compressed air coupled to said airbrush, a valve connected between said source of compressed air and the airbrush to control the application of compressed air thereto, and means coupled between said roller and said valve for opening said valve when said roller is engaged by any one of said elongated workpieces and for closing said valve when said roller is not engaged by one of said elongated workpieces.

4. Automatic air painting apparatus as defined in claim 3 wherein said means coupled between said roller and said valve comprises a solenoid attached to said valve for opening and closing the valve in response to electrical signals, an electrical switch coupled to said roller in such manner as to be actuated whenever said roller engages an elongated workpiece and to be deactuated whenever said roller is not engaged by one of said elongated workpieces, and electrical means coupled between said switch and said solenoid for actuating the sole' noid in response to the actuation of said switch.

5. Automatic air painting apparatus as defined in claim 4 wherein said roller is positioned to make direct contact with the nozzle of said airbrush to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces.

6. Automatic air painting apparatus as defined in claim 5 wherein said means for moving elongated workpieces past the nozzle of said airbrush comprises means defining a conveyor channel under said nozzle, a plurality of resilient drive rollers projecting into said conveyor channel, and means for rotating said drive rollers to drive said elongated workpieces through said conveyor channel.

7. Automatic air painting apparatus as defined in claim 6 and further comprising a plurality of resilient idler rollers projecting into said conveyor channel, each of said idler rollers being positioned opposite a corresponding one of said drive rollers, and spring means urging each of said idler rollers toward the corresponding drive roller to hold said elongated workpieces in contact with the drive roller as each workpiece passes between the drive roller and its opposing idler roller.

8. Automatic air painting apparatus as defined in claim 7 wherein the bottom of said conveyor channel is lined with a plastic material having a relatively low coefficient of friction for supporting said elongated workpieces as they are moved through said conveyor channel.

9. Automatic air painting apparatus as defined in claim 6 and further comprising a second airbrush having a nozzle and means for ejecting a flow of paint from said nozzle in response to the application of compressed air thereto, said second airbrush being journalcd to said supporting structure for rotation about an axis transverse to the axis of said nozzle, means defining a second conveyor channel under said second airbrush nozzle parallel to the first-mentioned conveyor channel, a second plurality of resilient drive rollers projecting into said second conveyor channel, means for rotating said second plurality of drive rollers to drive elongated workpieces through said second conveyor channel, means urging the rotation of said second airbrush about its journal axis toward said elongated workpieces, a second spacing roller positioned to be engaged by said elongated workpieces as they pass the nozzle of said second airbrush and to make direct contact with the nozzle of said second airbrush to maintain a predetermined spac ing between said nozzle and the adjacent surface of said elongated workpieces, and means coupled to said second spacing roller for applying compressed air to said second airbrush when said second spacing roller is engaged by any one of said elongated workpieces, thereby applying a flow of paint to the adjacent surfaces of said elongated workpieces as they are moved past the nozzle of said second airbrush.

10. Automatic air painting apparatus as defined in claim 9 wherein said means coupled to said second spacing roller for applying compressed air to said airbrush comprises means for coupling said source of compressed air to said second airbrush, a second valve connected between said source of compressed air and said second airbrush, a second solenoid attached to said valve for actuating the valve in response to electrical signals, a second switch coupled to said second spacing roller and positioned to be actuated when said roller is engaged by any one of said elongated workpieces and to be deactuated when said roller is not engaged by one of said elongated workpieces, and electrical means coupled between said second switch and said second solenoid for actuating said second valve in response to the actuation of said second switch.

11. Automatic air painting apparatus as defined in claim 10 and further comprising a plurality of resilient idler rollers projecting into said first and second conveyor channels, each of said idler rollers being positioned opposite a corresponding one of said drive rollers, and spring means urging each of said idler rollers toward the corresponding drive roller to hold said elongated workpieces in contact with the drive roller as each workpiece passes between the drive roller and its opposing idler roller.

12. Automatic air painting apparatus as defined in claim 11 wherein the bottoms of said conveyor channels are each lined with a plastic material having a relatively low coefficient of friction for supporting said elongated workpieces as they are moved through said conveyor channels.

13. Automatic air painting apparatus as defined in claim 12 wherein each of said drive rollers has a drive shaft depending downwardly therefrom and a drive pulley attached to said drive shaft, and wherein said means for rotating said drive rollers comprises a motor having a drive shaft, a drive pulley attached thereto, and belt drive means coupling the motor drive pulley to each of said roller drive pulleys.

14. Automatic air painting apparatus as defined in claim 13 and further comprising a common paint source coupled to both of said airbrushes. 

1. Automatic air painting apparatus comprising a supporting structure, an airbrush having a nozzle and means for ejecting a flow of paint from said nozzle in response to the application of compressed air thereto, said airbrush being journaled to said supporting structure for rotation about an axis transverse to the axis of said nozzle, means for moving elongated workpieces past the nozzle of said airbrush, means urging the rotation of said airbrush about its journal axis toward said elongated workpieces, a spacing roller positioned to be engaged by said elongated workpieces as they pass the nozzle of said airbrush, said roller being coupled to the nozzle of said airbrush and being operable to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces as they move past said nozzle, and means coupled to said roller for applying compressed air to said airbrush when said roller is engaged by any one of said elongated workpieces, thereby applying a flow of paint to said adjacent surfaces of said elongated workpieces as they are moved past the nozzle of said airbrush.
 2. Automatic air painting apparatus as defined in claim 1 wherein said spacing roller is positioned to make direct contact with the nozzle of said airbrush to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces.
 3. Automatic air painting apparatus as defined in claim 1 wherein said last-mentioned means comprises a source of compressed air coupled to said airbrush, a valve connected between said source of compressed air and the airbrush to control the application of compressed air thereto, and means coupled between said roller and said valve for opening said valve when said roller is engaged by any one of said elongated workpieces and for closing said valve when said roller is not engaged by one of said elongated workpieces.
 4. Automatic air painting apparatus as defined in claim 3 wherein said means coupled between said roller and said valve comprises a solenoid attached to said valve for opening and closing the valve in response to electrical signals, an electrical switch coupled to said roller in such manner as to be actuated whenever said roller engages an elongated workpiece and to be deactuaTed whenever said roller is not engaged by one of said elongated workpieces, and electrical means coupled between said switch and said solenoid for actuating the solenoid in response to the actuation of said switch.
 5. Automatic air painting apparatus as defined in claim 4 wherein said roller is positioned to make direct contact with the nozzle of said airbrush to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces.
 6. Automatic air painting apparatus as defined in claim 5 wherein said means for moving elongated workpieces past the nozzle of said airbrush comprises means defining a conveyor channel under said nozzle, a plurality of resilient drive rollers projecting into said conveyor channel, and means for rotating said drive rollers to drive said elongated workpieces through said conveyor channel.
 7. Automatic air painting apparatus as defined in claim 6 and further comprising a plurality of resilient idler rollers projecting into said conveyor channel, each of said idler rollers being positioned opposite a corresponding one of said drive rollers, and spring means urging each of said idler rollers toward the corresponding drive roller to hold said elongated workpieces in contact with the drive roller as each workpiece passes between the drive roller and its opposing idler roller.
 8. Automatic air painting apparatus as defined in claim 7 wherein the bottom of said conveyor channel is lined with a plastic material having a relatively low coefficient of friction for supporting said elongated workpieces as they are moved through said conveyor channel.
 9. Automatic air painting apparatus as defined in claim 6 and further comprising a second airbrush having a nozzle and means for ejecting a flow of paint from said nozzle in response to the application of compressed air thereto, said second airbrush being journaled to said supporting structure for rotation about an axis transverse to the axis of said nozzle, means defining a second conveyor channel under said second airbrush nozzle parallel to the first-mentioned conveyor channel, a second plurality of resilient drive rollers projecting into said second conveyor channel, means for rotating said second plurality of drive rollers to drive elongated workpieces through said second conveyor channel, means urging the rotation of said second airbrush about its journal axis toward said elongated workpieces, a second spacing roller positioned to be engaged by said elongated workpieces as they pass the nozzle of said second airbrush and to make direct contact with the nozzle of said second airbrush to maintain a predetermined spacing between said nozzle and the adjacent surface of said elongated workpieces, and means coupled to said second spacing roller for applying compressed air to said second airbrush when said second spacing roller is engaged by any one of said elongated workpieces, thereby applying a flow of paint to the adjacent surfaces of said elongated workpieces as they are moved past the nozzle of said second airbrush.
 10. Automatic air painting apparatus as defined in claim 9 wherein said means coupled to said second spacing roller for applying compressed air to said airbrush comprises means for coupling said source of compressed air to said second airbrush, a second valve connected between said source of compressed air and said second airbrush, a second solenoid attached to said valve for actuating the valve in response to electrical signals, a second switch coupled to said second spacing roller and positioned to be actuated when said roller is engaged by any one of said elongated workpieces and to be deactuated when said roller is not engaged by one of said elongated workpieces, and electrical means coupled between said second switch and said second solenoid for actuating said second valve in response to the actuation of said second switch.
 11. Automatic air painting apparatus as defined in claim 10 and further comprising a plurality of resilient idlEr rollers projecting into said first and second conveyor channels, each of said idler rollers being positioned opposite a corresponding one of said drive rollers, and spring means urging each of said idler rollers toward the corresponding drive roller to hold said elongated workpieces in contact with the drive roller as each workpiece passes between the drive roller and its opposing idler roller.
 12. Automatic air painting apparatus as defined in claim 11 wherein the bottoms of said conveyor channels are each lined with a plastic material having a relatively low coefficient of friction for supporting said elongated workpieces as they are moved through said conveyor channels.
 13. Automatic air painting apparatus as defined in claim 12 wherein each of said drive rollers has a drive shaft depending downwardly therefrom and a drive pulley attached to said drive shaft, and wherein said means for rotating said drive rollers comprises a motor having a drive shaft, a drive pulley attached thereto, and belt drive means coupling the motor drive pulley to each of said roller drive pulleys.
 14. Automatic air painting apparatus as defined in claim 13 and further comprising a common paint source coupled to both of said airbrushes. 